1. Field of the Invention
The present invention relates to a tempered glass plate, and especially, to a tempered glass plate with a thin plate thickness adapted for weight reduction of a vehicle in recent years.
2. Description of the Related Art
As for a window glass of a vehicle, a tempered glass plate has been used, so far. The tempered glass plate includes a compressive stress layer formed on the surface of the tempered glass plate; and a tensile stress layer at a middle portion in the thickness direction of the tempered glass plate. The tempered glass plate can be produced by applying a strengthening process to the surface of the glass plate in a high temperature state, for example, from 650° C. to 700° C. by blowing the air.
In recent years, to achieve weight reduction of a vehicle from a view point of fuel saving, there is a demand for a glass plate with a thin plate thickness that satisfies a safety standard required for the tempered glass for the vehicle.
Patent Document 1 and Patent Document 2 disclose a tempered glass plate, which is a glass plate with a thin plate thickness, and which satisfies the safety standard required for the tempered glass plate for the vehicle.